Semi-instantaneous or instantaneous jump display mechanisms for timepieces or scientific equipment are designed to display at least one value of a first magnitude in an aperture.
This value is discrete and changes upon a, generally periodic, jump controlled by a mechanism or by a signal.
The display of such a magnitude is often supplemented by displays of other magnitudes, either likewise by jumps or by other means, such as e.g. the positioning of hands facing a dial plate. Thus, document CH 691 833 A5 VACHERON & CONSTANTIN SA describes a display module with jump hours display and a retrograde minutes display, the mechanism of which is driven by the cannon pinion. This jump hours display comprises an aperture, through which a number carried by an hour disc is visible, and the retrograde minutes display comprises a hand that is out of centre in relation to the display module, wherein this hand cooperates with an arc-shaped graduation with an angular extent of less than 180°.
In general, when the period of the first magnitude is large in relation to those pertaining to other displays, the user knows to estimate the exact value of the first magnitude when the other displays allow him/her to observe that the moment of the jump is sufficiently distant to avoid any ambiguity. For example, if the first magnitude is the hour and another display magnitude is the minute, the user sees, depending on the position of the minute indicator, where one is in relation to the instant of the hour change jump, provided, however, that the minute indicator displays that the instant of this jump is sufficiently far away: for example, the user determines without effort a time of 11 hours 5 minutes or even a time of 11 hours 45 minutes. The situation becomes more tricky as the moment of the jump approaches, since the user does not have the means to know whether the jump is going to occur or if it has just occurred, above all if he/she has not looked at the display in the preceding instants. For example, if the user sees a display of a value 12 for the hour and a value 0 for the minutes, he/she cannot know if the real time is midday (in which case the jump has just occurred) or 12 hours 59 minutes (just before the 1 pm jump). There is no simple solution allowing the user to determine instantaneously if the jump has already taken place or is in progress.